Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 8a9d1ad85b27bc14…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: cf9706e140f54f74d06fd882ced93a47 SHA-1: ea5c023c12e903499c30d7f96326f0b9c74c2420 SHA-256: 8a9d1ad85b27bc144db94bb32bc67d68bec983d1ebfd82d0a2983620b6ebe995
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1105 Ingress Tool Transfer

The file is an Excel 4.0 macro-enabled spreadsheet. Critical heuristics indicate the presence of WinAPI and download strings within the macro sheet, specifically mentioning functions like URLDownloadToFileA, DownloadToFileA, and ShellExecuteA. This strongly suggests the macro's purpose is to download and execute a secondary payload from a remote source. The macro sheet itself is heavily truncated, preventing a more detailed analysis of the specific download URL or execution path.

Heuristics 2

  • Excel 4.0 macro sheet (1 sheet(s)) critical OOXML_XLM_MACROSHEET
    Spreadsheet contains an Excel 4.0 (XLM) macro sheet — XLM was a major Office malware vector during 2020-2022 and evaded many VBA-focused controls before Microsoft tightened XLM defaults. Even legitimate XLM use is rare in modern workbooks. The macro sheet is stored as XLSB/BIFF12 binary content, which many XML-only OOXML scanners miss.
  • Binary XLM macro sheet with WinAPI/download strings critical OOXML_XLM_BINARY_WINAPI_STRINGS
    Excel 4.0 macro sheet is stored as BIFF12/XLSB binary data and contains Win32 download or process-execution API strings such as URLDownloadToFileA, ShellExecuteA, or CreateDirectoryA. These strings are high-signal in XLM macro sheets and catch payload-download macros that XML-formula scanners cannot parse.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
99a6a52acb8f5c734f6d86faf89e0637a94ac99f953aa583d2658b47d2e1f9b9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 194023 bytes

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